Background: Delirium is an acute cognitive disorder with features of inattention, disorganized thinking, and disordered consciousness that occurs in one third of hospitalized older adults. As compared to those without delirium, hospitalized patients with delirium have longer hospital stays, higher mortality, and increased risk of nursing home utilization. Substantial attention has been paid to developing, testing, and disseminating interventions to prevent delirium in the hospital but, to date, not in the nursing home setting. Ina previous study we used known information on delirium risk factors to develop a multicomponent intervention that can be delivered at onset of acute illness in nursing home patients. We demonstrated the intervention's feasibility, adherence, and acceptance by patients and staff. The current application proposes to test the efficacy of this intervention in a single-site cluster randomized trial. Objectives: 1) to determine, as compared to control, the effect of a multicomponent intervention targeting delirium risk factors (immobility, cognitive impairment, dehydration, undernutrition, sleep, and medication use) on the primary outcome of delirium frequency in nursing home patients with acute illness, and the secondary outcomes of delirium severity, cognitive and physical function decline, and hospitalization associated with acute illness, and 2) to identify features of the intervention, including dose and components, associated with occurrence of delirium and its severity, cognitive and physical function decline, and hospitalization associated with acute illness. Approach: We will screen nursing home patients on 17 long-term care units at a large, urban nursing home who experience onset of an acute change in condition according to established criteria, and enroll and assign them to intervention or control in a 1:1 ratio. Those assigned to intervention will receive daily visits frm an Elder Life Specialist, a mobile Certified Nursing Assistant trained to provide services to counter risks for delirium, including dehydration, immobility, cognitive impairment, undernutrition, and sleep problems, for the duration of the acute illness and for 1 week following, in collaboration with the patient's primary medical and nursing team. Patients assigned to control will receive usual care from the unit-based nurses and the patient's primary team. Delirium will be assessed 5 days a week by a research assistant blinded to study hypotheses and group assignment. Cognitive and physical function decline and hospital transfer will be ascertained during a 1 month follow-up period. We will conduct analyses to compare outcomes between intervention and control, as well as examine associations between outcomes and intervention features such as number and duration of visits.